Bletchley Park's Colossus codebreaker to race modern PC in cracking Nazi codes

Tony Sale and a group of British vintage computer enthusiasts is rebuilding Colossus, the gigantic proto-computer that Alan Turing and the Bletchley Park scientists built to crack German codes during WWII. The original Colossus machines were all broken up (into pieces "no bigger than a man's hand"!) after the war for security reasons, but Sale has tracked down the surviving Colossus engineers and is making great strides in completing the machine.

The finished Colossus is to be pitted against a contemporary general-purpose PC in a code-breaking race. The raw fodder for the race is a set of messages encrypted using Nazi ciphers and transmitted by amateur radio enthusiasts in Germany.

It's all in support of a new National Museum of Computing, based at Bletchley. What a cool idea -- I'm now officially planning a day-trip to Bletchley to see the museum.

He had no working machines to look at because, on Churchill's orders, the Colossus machines were dismantled once the war was over. Many parts, mostly the 1500 valves, went back to telephone exchanges and the rest were broken into pieces "no bigger than a man's hand".

Mr Sale has tracked down the few living engineers who worked on the project and plumbed their expertise to guide the rebuilding effort...

The German participants in the code-cracking challenge will transmit three enciphered messages - one hard, one very hard and one ultra hard.

The BBC's Rory Cellan-Jones said there was a "busy and business-like" atmosphere at Bletchley as the code cracking attempts got underway.

"We've seen webcam video of the Germans preparing to send the first signals," he said.

Link to BBC Colossus reborn story, Link to BBC crypto race story (via Futurismic)


  1. I had the happy privilege of seeing Colossus in action last year. It’s a truly badass machine – retrotech heaven! Tony Sale is one of the nicest and smartest fellows in the UK, and he was kind enough to chat in great detail about the project. He had been racing the Colossus against a Pentium 2 laptop – Colossus was beating it handily!

  2. This is so cool! I’d love to see one of these running.

    I’m actually amazed that it was dismantled after the war. I mean, couldn’t it have continued to be of use to intelligence bureaus ? Or was it seen as some sort of dead-end?

  3. @Thorzdad, the colossus wasn’t a general purpose computer such as modern PCs. It was essentially a big calculator capable of running only one hard-wired algorithm. Programming it was via a patch panel, which switched different circuits in and out.

    It was purpose built to speed up cracking of the Lorenz cipher, and once this was no longer needed, colossus could not be repurposed to other tasks.

    I wrote an essay a while ago comparing Colossus, Mark I and Zuse Z4, if your interested in early computers.

  4. I live only a few miles from bletchley Park and think it’s fantatsic – I have annual membership.

    If you do visit, try and find a day when Tony Sale is there and leading the tour as his knowledge and enthusiasm is wonderful.

    If you want any local info please feel free to drop me an email.


  5. I am curious how head on the museum will address how Turing was driven to suicide by government actions due to him being a “nancy boy” as they term homosexuals there.

  6. John Henry was lying on his death bed,
    He turned over on his side,
    And these were the last words John Henry said
    “Bring me a cool drink of water before I die.”

  7. TSOL @10: Radio-interception, and that was the actual messages rather than the codes; Colossus was built to crack the codes, using algorithms derived by pencil, paper and wetware. So Germany wouldn’t even have a case under copyright law, since it’s certainly fair use to record radio for your own use. Especially when it’s being transcribed by hand. (See Battle of Wits, by Stephen Budiansky.)

  8. Bletchley is great! Fun for the entire nerd family.

    Dybbuk: for the real American fifth column, read up on British Security Coordination.

    Mikelotus: I always understood that Turing was treated pretty well at Bletchley. It was post-WW2 Army strictures and archaic anti-homosexuality laws that got him.

  9. @Mikelotus: Ian Holmes has it right. It was only after the war that the government started abusing him, which is incredibly sad given that he could be considered a great war hero. It wasn’t until 1952 in fact.

  10. Ask any audiophile, valves are Warm. I’d go there just to be in the same room with 1500 valves.

    Like the Funk Brothers, it’s good to see, at long last, these erstwhile chappies getting their nod. Pip pip chappies!

  11. I went to Bletchly this summer and saw the rebuilt Colossus. It’s pretty much as awesome as it seems – they even have some vacume tubes from the origional machines (or…from the same time as the origional? I don’t recall).

    In any case, at the time they had a version of the code breaking system runnin on a laptop (I think it was an older powerbook) and the Colossus, once it had warmed up, kicked the laptop’s ass.

    I think it’ll be an interesting contest.

  12. They’re going to rebuild Colossus! The Fools! Don’t they realize that it will join with the Soviet Guardian system and take over the word!

    Oh wait, you mean the *other* Colossus…….

    That was a pretty cool machine. It was used to decrypt German teletype codes, as opposed to the better known Enigma radio codes, once the Alliies were in the E.T.O. after D-day. They originally tried to do this with a mechanical system that spun teletype tapes around at 30 miles per hour XORing German messages with those same messages offset from the originals to varying degrees. You knew that you had a good guess when some section of result had a lot of zeros in it. Problem was that the tapes tended to stretch so you often wasted runs because the slippage screwed with the banks of photoelectric cells that were watching for a good run of zeros.

    So they expanded on the idea of using vacuum tubes that they’d come up with in the course of building one of the monstrous Steam Punk engines that was working on the Naval Enigma problem. Over there they had a set of six mechanical Enigma “Bombs” (mechanical simulations of Enigma wheel settings as applied to a specific intercepted message) being cranked along through a series of related key guesses by a central shaft at several hundred RPM. Once a regular pattern was detected in their output you had to stop the whole works and read off the current set of guesses to some human who had to see if the regular pattern amounted to German Military Speak or was just statistical clustering. Problem was that mechanical relays often were too slow to keep up with the whirly gears at anything past half speed. Even then a relay might stick and produce a false positive that could waste a half-hour while you applied the brakes and then carefully rewound to the spot where the the pattern had seemed to emerge.

    So they invented the idea of using vacuum tubes as memories storing the instantaneous output of the Bombs for the fraction of a second that it took for the Pondering Circuits to see if the pattern that they were looking for was there. They were, even back then, more reliable than the best relays so you saved a lot on time and brake pads due to lower number of false positives. Best of all, you could really pour on the horsepower to the central shaft as the tubes could jump to each new set of outputs way faster than the relays could.

    So they went from the idea of storing readouts from physical reality in tubes to storing simulations of physical reality (the teletype tapes and their relative positions) in Colossus. Thus was the first VR born!

    The Mark I had 1,500 tubes but later models got up to 2,500.

    (See Battle of Wits, by Stephen Budiansky.)

  13. I think you give Turing too much credit. The man who actually built the colossus was Tommy Flowers. Turing was still trying to get an electromechanical computer to work reliably (which it never did).

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